Inhibition of corrosion of metals



33,159/63 US. Cl. 25275 Int. Cl. C09k 3/00; Clld 1/00 13 Claims ABSTRACT OF THE DISCLOSURE Methods and compositions for inhibiting corrosion in liquid-containing metal systems are provided by the use of a water-soluble condensation product of an aminoalkyl silicate and an oxirane compound possessing one oxirane grouping. The product is particularly etlective in such systems which utilize aluminium or aluminium-containing alloys in their construction.

This invention relates to improvements in methods of inhibiting the corrosion of metals, and is particularly concerned with the inhibition of corrosion in liquid-containing metal systems.

The corrosion of liquid-containing metal systems is in general due to contact of the metal with water in the presence of air. Corrosion is a particularly severe problem in systems which contain a circulating liquid comprising water, as is generally the case in cooling systems such as those used in internal combustion engines. Corrosion may also occur, however, in systems containing an essentially organic liquid, for example in hydraulic brake systems using a liquid such as a polyethylene glycol monoether as hydraulic fluid, due to the presence of water in small proportions either by design or accident e.g. by leakage into the system or by absorption from the atmosphere.

In cooling systems for internal combustion engines. it is common practice to add to the water in the system an anti-freeze composition which depresses the freezing point of the water below C. A number of anti-freeze compositions are available which in general contain ethylene glycol as principal ingredient. Used alone, however, a water/ethylene glycol mixture tends to be even more corrosive than water itself. It is also common practice, therefore, to incorporate in these liquids small amounts of other compounds which serve as corrosion inhibitors. Different compounds act as corrosion inhibitors for ditferent metals, and, as it is usual for the cooling systems of internal combustion engines to incorporate a variety of metals, two or more compounds are normally needed to provide adequate overall protection. Thus, sodium mercaptobenzothiazole or benzotriazole is useful as a corrosion inhibitor for copper, sodium benzoate as an inhibitor for mild steel and sodium benzoate together with sodium nitrite as an inhibitor for cast iron.

A disadvantage with many of the previously proposed corrosion inhibitors is that they give insufficient protection to aluminium and aluminium-containing alloys. Inorganic silicates do however give some protection to such metals but suffer from the disadvantage that those which are adequately soluble in antifreeze liquids such as ethylene glycol are highly alkaline giving in solution a pH of 11 or greater. Such alkaline solutions are highly objectionable, principally because the high alkalinity reduces the efficiency of the protection afforded to the aluminium and aluminium-containing alloys. A further disadvantage of inorganic silicates is that they precipitate calcium and magnesium from hard water. It is an object of the present nited States Patent 0 "ice invention to provide an improved method of inhibiting the corrosion of aluminium and aluminium alloys.

According to one feature of the invention, therefore, there is provided a method of inhibiting the corrosion of a waterand/or organic liquid-containing metal system in which there is included in the liquid contained in the system a condensation product of an aminoalkyl silicate and an oxirane compound possessing one oxirane grouping, that is the grouping the condensation product being soluble in the liquid contained in the system to give a stable solution (as hereinafter defined).

By the term stable solution as used herein in relation to aqueous solutions, we mean a solution which does not separate to give a precipitate or sludge. By the term stable solution as used herein in relation to solutions comprising an organic liquid as solvent, we mean a solution which does not give rise to a precipitate or sludge when mixed with water.

It will be appreciated that, whilst the method according to the invention is particularly adapted to the inhibition of metal systems incorporating aluminium and aluminium alloys, it is nevertheless useful for the protection of systems which are made exclusively of metals other than aluminium. Thus, for example, the corrosion of cast iron is inhibited by the method of the invention. The protection of aluminium and aluminium alloys is an important feature of the invention, the said condensation products having the advantage of giving rise to pHs of relatively low alkalinity and conferring a high degree of protection on the metal. The condensation products also have the advantage of not precipitating in hard water. Furthermore, in solutions which do have high alkalinity, the said condensation products afiord a measure of protection of aluminium and aluminium containing alloys.

One convenient condensation product for use in the method according to the invention is that obtainable by the condensation of tetra-(monoethanolamine) orthosilicate [Si(OC H NH with 2 mols. of butylene oxide per NH grouping. This compound is water stable (that is stable to hydrolysis by water) and it is believed that in general it may possibly be advantageous to use waterstable condensation products in the method of the invention. Whilst not wishing to be bounded by theoretical considerations, it appears probable that the water stability of the tetra-(monoethanolamine) orthosilicate/butylene oxide product results from a steric effect, the hydroxyalkyl groups of the condensation product serving by means of steric hindrance to exclude water from the inner hydrolysable part of the molecule.

Suitable aminoalkyl silicates for use in the preparation of the condensation products are described in United States patent specification No. 3,110,601. Thus, the aminoalkyl silicates can be orthosilicates of the general formula Si(OR (OR where R is an alkyl group carrying an amino group having one or two hydrogen atoms attached to the nitrogen atom, R is an unsubstituted alkyl group and x has the value 1, 2, 3 or 4; they can be polysilicates of the empirical or unit formula (R O) (R O) SiO where R, and R have the above meanings and y has a value greater than zero and up to 2; or they can be a mixture of orthosilicates and polysilicates.

The aminoalkyl groups R of the silicate are suitably those derived from an aminoalcohol of the formula R .N.HR where R represents a hydroxyalkyl group containing 1 to 6 carbon atoms; and R represents hydrogen, or an alkyl or monohydroxyalkyl group containing 1 to 6 carbon atoms; the number of hydroxyl groups of the alcohol not exceeding two. Preferred aminoalkyl groups are those derived from an alcohol of the above formula in which R, contains 2 to 4 carbon atoms and one hydroxyl group and R represents an alkyl or monohydroxyalkyl group with 1 to 4 carbon atoms or, most preferably, hydrogen; where R represents a hydroxyalkylgroup, it preferably contains only two or three carbon atoms. As stated above, one aminoalkyl silicate which may conveniently be used is tetra (mon-oethanolarnine) orthosilicate. Other silicates which may be used include the following tetra (aminoalkyl) orthosilicates:

Tetra-(Z-amino-but-l-yi) orthosilicate [Si(OCI'I2.CH.NH2.CH2.CH3)4] and tetra- (monoisopropanolamine orthosilicate [Si(O.C I-l .NH Particularly suitable polysilicates include tetra (monoethanolamine) and tetra (isopropanolamine) polysilicates.

The aminoalkyl silicate should be reacted with a suitable oxirane to give a condensation product soluble in the liquid to which it is to be added to yield a stable solution (as hereinbefore defined). Oxiranes which are conveniently used include compounds of the formula wherein R and R which may be the same or different each represent hydrogen or a saturated or unsaturated aliphatic group with l to 6 carbon atoms; a phenyl group; an alkylphenyl group of which the alkyl radical contains 1 to 6 carbon atoms; or a benzyl group; which groups may be substituted provided that any such substituent is not reactive with an amino group of the amino alkyl silicate. R and R preferably represent hydrogen,

alkyl groups such as methyl, ethyl, n-propyl, isopropyl or hexyl groups; alkenyl groups such as vinyl, allyl, propl-enyl or but-l-enyl groups; phenyl groups or alkyl-phenyl groups such as toluyl, ethyl phenyl, n-propylphenyl or n-butyl phenyl groups; or benzyl groups. Examples of convenient oxirane compounds include 1,2-butylene oxide, 2,3-butylene oxide, glycidol, styrene oxide, allyl glycidyl ether and 1,2-epoxy-3-phenoxy-propane. Preferred oxiranes include ethylene oxide, propylene oxide or, most preferably, a butylene oxide.

The condensation products used in the method according to the invention are preferably prepared by condensing an aminoalkyl silicate having primary or secondary amino groups with an oxirane. The reaction conditions for this condensation, and also processes for the preparation of the aminoalkyl silicates used as starting materials therefor, are described in United States patent specification No. 3,110,601.

In cases where the amino-alkyl silicate employed in the condensation contains unsubstituted organic groups, for example methoxy or ethoxy groups, and the condensation reaction is performed by heating, the silicate-oxirane condensate obtained may undergo a self-condensation reaction as described in United States patent specification No. 3,110,601. The use of the self-condensation products thereby obtained is intended to be within the scope of the present invention.

One particular application of the method according to the invention is in relation to heat exchange systems e.g. the cooling systems of internal combustion engines utilising an exchange fluid comprising water. In such systems, the condensation product will preferably be added to the exchange fluid in a proportion in the range of from 0.01 to 1%, advantageously from 0.02 to 0.50%, particularly about 0.06%, by weight. A proportion of condensation product greater than 1% by weight may if desired be used but will in general be uneconomical. Also, it will generally be desirable to incorporate in the exchange fluid other compounds which serve as corrosion inhibitors. Suitable such compounds include the followmg:

(l) Alkali metal salts of carboxylic acids, which include, for example, salts of:

(a) Aromatic acids such a phthalic, l-naphthoic, 2- naphthoic or, most preferably, benZ-oic acid. Sodium benzoate is a preferred additive of this type.

(b) Alkyl-substituted aromatic acids, particularly such acids with the alkyl group in a position para to the carboxylic acid group. A suitable acid of this type is 4-methyl benzoic acid.

(c) Alkoxy substituted aromatic acids, particularly such acids with the alkoxy group in a position para to the carboxylic acid group. A suitable acid of this type is anisic acid.

(d) Unsubstituted acids which have been produced by the partial or complete hydrogenation of aromatic acids such as benzoic acid, l-naphthoic acid and Z-naphthoic acid. A suitable acid of this type is hexahydrobenzoic acid.

(e) Acids as in (d) which bear alkyl or alkoxy groups, particularly in a position para to the carboxylic acid group. Of the cis and trans compounds which exist in compounds of this type, the trans compound is preferably employed. A suitable acid of this type is trans 4-rnethyl cyclohexane carboxylic acid.

(f) Acids in which an aromatic group is separated from a carboxylic acid group by an aliphatic grouping such as one or more methylene groups or a group of the type CH=CH--. Examples of acids of this type are phenylacetic and cinnamic acid.

(g) Acids as in (f) containing an alkyl or alkoxy group in a position para to the carboxylic acid substituted aliphatic group.

(h) Acids as in (f) or (g) in which the aromatic nucleus has undergone partial or complete hydrogenation. Hexahydrophenylacetic acid and 2-cyclohexyl-propionic acid are suitable acids of this type. In general, when an alkyl or alkoxy group is present in the cyclic ring in a position para to the group containing the carboxyl radical, cis and trans isomers exist. Of these, it is preferable to use the trans isomer.

(i) Acids of the formula ArOCH .COOH, wherein Ar represents an aromatic radical which may, for example, be a phenyl, l-naphthyl or Z-naphthyl group. When a phenyl group is present, this may contain alkyl or alkoxy groups in the 4-position to the O.CH .COOH groups. Particularly suitable compounds are 4-octyl and 4-nonylphenoxyacetic acids. The octyl group may be, for example, that derived from propylene trimer. Other acids of this type which may be used include Z-naphthoxy-acetic acid and 4-methylphenoxy-acetic acid.

(j) The cyclohexyl ether of glycolic acid, or substituted derivatives thereof containing alkyl or alkoxy groups, preferably in the 4-position to the OCH .COOH group. These 4-substituted derivatives exist in general as cis and trans isomers and of these it is preferable to employ the trans isomer. Cyclohexyl glycolic acid is an example of an acid of this type.

(k) Acids as in (j) except that hydrogenated aromatic radicals other than cyclohexyl are employed. One example of an acid of this type is decahydro-Z-naphthoxyacetic acid.

These additives are preferably in the form of the sodium salts.

(2) Soluble nitrites, preferably alkali metal nitrites such as, for example, sodium nitrite.

(3) A copper de-activator such as, for example, sodium mercaptobenzothiazole or, most preferably, benzotriazole.

(4) An alkali metal borate e.g. sodium borate. The sodium borate may be employed in any suitable form, and may for example be introduced as octahedral borax [Na B O 5H O] or as monoclinic borax (5) A phosphate such as, for example, triethanolamine phosphate.

In addition to the above-mentioned corrosion inhibitors it is common in cooling systems such as those used in internal combustion engines to add to the Water used as exchange fluid a water-miscible organic liquid which depresses the freezing point of the water below C. It will in general be convenient to add the water-miscible organic liquid, the condensation product of the aminoalkyl silicate and the oxirane, and any other desired corrosion inhibitors in the form of a single anti-freeze composition.

According to one feature of the invention, therefore, there is provided an anti-freeze composition suitable for addition to exchange liquids comprising water in a heat exchange system which comprises a stable solution (as hereinbefore defined) of a water-soluble condensation product of an aminoalkyl silicate and an oxirane compound posessing one oxirane grouping in a water-miscible organic liquid. Preferred water-miscible organic liquids for use as freezing point-depressants are hydroxylic organic solvents, particularly glycols such as, for example, diethylene glycol, propylene glycol, hexylene glycol and, most preferably, monoethylene glycol. Other organic liquids which may conveniently be used include aliphatic alcohols such as methanol, ethanol, propanol, isopropanol and glycerol.

The silicate/oxirane condensation product will preferably be present in the water-miscible organic liquid in a proportion in the range of from 0.05 to 2% by weight. The anti-freeze composition may also in addition contain one or more further corrosion inhibitors for example the corrosion inhibitors mentioned above in the paragraphs numbered 1 to 5. The preferred proportions of such additives present in the compositions according to the invention are as follows:

Additives listed under: Percent by Weight The anti-freeze composition according to the invention may also if desired contain a colouring agent and/or a pH indicator whereby a check may be kept upon the alkalinity of the exchange fluid to which the anti-freeze composition is added.

The method according to the present invention may be utilized in ways other than by the addition of anti-freeze compositions to exchange liquids in heat exchange systems. Thus, for example, in heat exchange systems which utilise water as exchange liquid and which are not liable to be subjected to temperature below 0 C., for example in the cooling systems of internal combustion engines or industrial plants used under mild climatic conditions, it may still be desirable to include corrosion inhibitors. It is often useful therefore to add corrosion inhibitors alone to the exchange fluid without also incorporating a Watermiscible organic liquid, such additions for example, being frequently made during the summer months purely to inhibit corrosion of the system.

Also, leak sealing compositions are known for addition to exchange liquids in metal systems; such compositions in general comprise a fine suspension of insoluble material in water, the insoluble material serving to seal any leak which may occur in the system. Such compositions may remain in the system for some time and it is thus often desirable to include therein corrosion inhibitors.

According to a further feature of the invention, therefore, there is provided a composition suitable for incorporation into aqueous liquids in a metal system which comprises an aqueous solution containing 1) a watersoluble condensation product of an aminoalkyl silicate and the oxirane compound possessing one oxirane grouping and (2) at least one other compound having corrosion-inhibiting properties. The quantity of condensation product in the composition will in general preferably be in the range of from 0.05 to 15%, particularly 0.5 to 1.5%, and especially about 1.0%, by weight. The other corrosion-inhibiting compound may, for example, be any of the compounds listed above in the paragraphs (1) to (5). A particularly convenient borate for this purpose in sodium metaborate, which is soluble in water to an extent suificient to enable a concentrate to be prepared. One suitable composition consists of water containing about 1.0% by weight of condensation product, about 20% by weight of sodium benzoate and about 2% by weight of sodium nitrite. The compositions may for example be added to exchange liquid in a metal system, e.g., in a proportion of 1 part of composition to about 10 parts of exchange liquid. These compositions according to the invention may also if desired contain a fine suspension of insoluble material (i.e., be leak sealing compositions).

A further application of the method according to the invention is in the field of cleaning compositions for metal systems. Such cleaning compositions are known which comprise a highly alkaline salt e.g., trisodium phosphate or sodium carbonate in water; when circulated hot such compositions loosen oil-bound rust and products of corrosion. Again, corrosion inhibitors are usefully included in such compositions, particularly inhibitors effective against aluminium corrosion. According to a still further feature of the invention, therefore, there is provided a cleaning composition for metal systems which comprises an aqueous solution containing (1) a water-soluble condensation product of an aminoalkyl silicate and an oxirane compound possessing one oxirane grouping, and (2) a highly alkaline salt, e.g., trisodium phosphate or sodium carbonate. These compositions may conveniently contain from 2 to 40%, preferably about 25% by weight of the highly alkaline salt.

The method according to the invention is also applicable to the inhibition of corrosion in organic liquidcontaining metal systems which either by design or accident may contain a small proportion of Water. Hydraulic systems such as hydraulic brake systems provide examples of such systems. Hydraulic brake systems may thus contain a small proportion, e.g., up to 2% by Weight of water, and when water is not specifically added the hydraulic fluid nevertheless frequently becomes contaminated with Water in use. It is, therefore, desirable to protect such metal systems against possible corrosion, and the present invention further provides a hydraulic fluid composition comprising a stable solution (as hereinbefore defined) of a condensation product of an aminoalkyl silicate and an oxirane compound possessing an oxirane group, in an organic hydraulic liquid. Suitable organic liquids for use in hydraulic, e.g., hydraulic brake, systems include water miscible organic liquids such as, for example, monoethylene-, polyethylene-, monopropyleneand polypropylene- .glycols and glycol monoethers of various chain lengths.

Examples of especially suitable organic liquids are monoethylene glycol and monomethyl, monoethyl and monobutyl ethers thereof, monopropylene glycol and monomethyl, monoethyl and monobutyl ethers thereof, dipropylene glycol and monomethyl, monoethyl and monobutyl ethers thereof, triethylene glycol and monomethyl, monoethyl and monobutyl ethers thereof and triprop-ylene glycol and monomethyl, monoethyl and monobutyl ethers thereof. One particularly useful hydraulic brake fluid comprises diethylene glycol monomethyl ether and diethylene glycol, preferably with a small proportion of a lubricant. One particularly convenient hydraulic brake fluid comprises 70-80% of diethylene glycol monomethyl ether along with 10-30% of a lubricant such as castor oil (either blown or unblown) or a polyglycol co-polymer. The proportion of condensation product is preferably in the range of from 0.01 to 2% by weight based upon the weight of organic liquid; higher proportions may if desired be used but are in general uneconomical. Again, the hydraulic fluid may contain further corrosion-inhibiting compounds as described above, provided such further compounds are soluble therein. Alkali metal nitrites are insoluble in organic hydraulic fluids such as diethylene glycol monomethyl ether and may therefore not be used for this purpose. Other suitable additives for this purpose include bisphenol A, alkyl-substituted imidazoles and hydroquinone. The latter are anti-oxidants which inhibit the breakdown of hydraulic fluids.

The following examples illustrate the invention:

EXAMPLE 1 An anti-freeze composition is prepared having the following composition (wherein all parts are by weight):

Parts Ethylene glycol 88.665 Benzotriazole 0.200 Rosolic acid 0.005 Tetra (monoethanolamine) orthosilicate/butylene oxide condensate (2 mols per NH group) 0.250 Sodium nitrite 1.000 Sodium benzoate 7.000 Water 2.880

The tetra-(monoethanolamine) orthosilicate/butylene oxide condensate was prepared as described in Example 21 of United States patent specification No. 3,110,601. Thus, 67 g. of tetra-(monoethanolamine) orthosilicate (0.25 mol) and 144 g. of butylene oxide isomers (2 mols) were condensed *by heating them under reflux for 2 hours. (The butylene oxide consisted of a mixture of the normal isomers 1,2-butylene oxide and 2,3-butylene oxide present in the ratio 4:1.) Refluxing then ceased and heating was continued for a further hour. There was no loss of butylene oxide during the heating. The product was a yellow oil miscible with water. The amount of oxide employed corresponded to 2 mols per NH group of the silicate.

EXAMPLE 2 A summer inhibitor composition is prepared having the following composition (wherein all parts are by weight):

Parts Sodium metaborate 15.0

Benzotriazole 0.25 Tetra- (monoethanolamine) orthosilicate/butylene oxide condensate (2 mols per NH group) 1.2

Water 83.55

250 millilitres of this composition when added to 5 litres of water afford corrosion protection to an automobile radiator system.

EXAMPLE 3 A hydraulic brake fluid is prepared having the following composition (wherein all parts are by weight):

Tetra (monoethanolamine)orthosilicate/butylene oxide condensate (2 mols per NH group) 0.50

Similar compositions to those described in Example 1 may be prepared substituting the condensation product employed therein by the condensation products of Examples 1B, 1C, 4, 10, 14, 19 and 21 of United States patent specification No. 3,110,601.

Similar compositions to that described in Example 3 may be prepared substituting the condensation product employed therein by the condensation products of Examples 1B, 1C, 2, 3, 4, 9, 10, 11, 14, 19, 21 and 24 of United States patent specification No. 3,110,601.

EXAMPLE 4 Cooling system cleaning composition Parts by weight Trisodium phosphate 25.00

EXAMPLE 4-Continued Parts by weight Tetra (monoethanolarnine) orthosilicate/ butylene oxide condensate (2 mols per NH group) 2.50 Water 72.50

The composition is added to the cooling system in the ratio of 500 millilitres per 5 litres of coolant.

We claim:

1. A method of inhibiting the corrosion of a metal system containing water and a water-miscible organic solvent selected from the group consisting of a lower alkylene glycol, a poly lower alkylene glycol, a lower alkanol, a lower polyol, a lower alkylene glycol mono lower alkyl ether and a poly lower alkylene glycol mono lower alkyl other which comprises adding to said solvent from 0.01 to 1% by weight of a condensation product of an aminoalkyl silicate selected from the group consisting of a silicate of the formula wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl group of from 1 to 6 carbon atoms and x is an integer of from 1 to 4 and a silicate of the formula (R O) (R O) SiO, wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl of from 1 to 6 carbon atoms and y has a value greater than zero and up to 2 and an oxirane compound of the formula RCH-CHR1 wherein R and R are each selected from the group consisting of hydrogen, alkyl of from 1 to 6 carbon atoms, alkenyl of from 1 to 6 carbon atoms, a phenyl group, an alkyl-phenyl group wherein the alkyl group is of 1 to 6 carbon atoms and a benzyl group, said condensation product being soluble and stable in the liquid contained in said system.

2. A method as claimed in claim 1 in which said condensation product is the product of the condensation of tetra-(monoethanolamine) orthosilicate with butylene oxide.

3. A method according to claim 1 wherein said condensation product is obtained by condensing tetra-(monoethanolamine) orthosilicate with 2 moles of butylene oxide per NH grouping of said orthosilicate.

4. An antifreeze composition suitable for addition to water employed as a heat exchange liquid which consists essentially of from 0.5 to 2% by weight of a water soluble condensation product of an aminoalkyl silicate selected from the group consisting of a silicate of the formula Si(OR (-OR wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl group of from 1 to 6 carbon atoms and x is an integer of from 1 to 4 and a silicate of the formula (R O) (R O) SiO, wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl of from 1 to 6 carbon atoms and y has a value greater than zero and up to 2 and an oxirane compound of the formula R-CH' CHR1 wherein R and R are each selected from the group consisting of hydrogen, alkyl of from 1 to 6 carbon atoms, alkenyl of 1 to 6 carbon atoms, a phenyl group, an alkyl-phenyl group wherein the alkyl group is of 1 to 6 carbon atoms and a benzyl group in a water-miscible organic solvent selected from the group consisting of a lower alkylene glycol, a poly lower alkylene glycol, a

lower alkanol and a lower polyol, said composition forming a stable solution when added to water.

5. A composition as claimed in claim 4 wherein the condensation product is a product of the condensation of tetra-(monoethanolamine) orthosilicate with said oxirane compound.

6. A composition as claimed in claim 4 in which said oxirane compound is butylene oxide.

7. A composition according to claim 4 wherein said condensation product is the product of the condensation of an aminoalkyl silicate wherein the aminoalkyl group thereof possesses the formula wherein R is an alkylene of from 1 to 6 carbon atoms and R is selected from the group consisting of alkyl of from 1 to 6 carbon atoms and monohydroxy alkyl of from 1 to 6 carbon atoms with said oxirane compound.

8. An antifreeze composition according to claim 4 wherein said condensation product is the condensation product of tetra-(monoethanolamine)orthosilicate and butylene oxide and said oxide is reacted in an amount of 2 moles for each NH group of said orthosilicate.

9. An antifreeze composition according to claim 4 wherein said water miscible organic solvent is monoethylene glycol.

10. An antifreeze composition according to claim 4 which contains at least one corrosion inhibitor selected from the group consisting of an alkali metal salt of benzoic acid, an alkali metal salt of phthalic acid, an alkali metal salt of naphthoic acid, an alkali metal salt of hexahydrophenylacetic acid, an alkali metal salt of 2-cyclohexyl-propionic acid, an alkali metal salt of cyclohexyl ether of glycollic acid, an alkali metal salt of decahydro- Z-naphthoxy-acetic acid, an alkali metal nitrite, sodium mercaptobenzothiazole, benzotriazole, an alkali metal borate and triethanolamiue phosphate.

11. A composition suitable for incorporation into aqueous liquids in a metal system, said composition consisting essentially of an aqueous solution containing (1) from 0.05 to 15% by weight of a water-soluble condensation product of an aminoalkyl silicate selected from the group consisting of a silicate of the formula wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl group of from 1 to 6 carbon atoms, and x is an integer of from 1 to 4 and a silicate of the formula (R O) (R O) SiO, wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl of from 1 to 6 carbon atoms and y has a value greater than zero and up to 2 and an oxirane compound of the formula wherein R and R are each selected from the group consisting of hydrogen, alkyl of from 1 to 6 carbon atoms, alkenyl of 1 to 6 carbon atoms, a phenyl group, an alkyl-phenyl group wherein the alkyl group is of 1 to 6 carbon atoms and a benzyl group and (2) at least one corrosion inhibitor selected from the group consisting of an alkali metal salt of benzoic acid, an alkali metal salt of phthalic acid, an alkali metal salt of naphthoic acid, an alkali metal salt of 2-cyclohexyl-propionic acid, an alkali metal salt of hexahydrophenylacetic acid, an alkali metal salt of 2-cyclohexyl-propionic acid, an alkali metal salt of cyclohexyl ether or glycollic acid, an alkali metal salt of decahydro 2 naphthoxy acetic acid, an alkali metal nitrite, sodium mercaptobenzothiazole, benzotriazole, an alkali metal borate and triethanolamiue phosphate.

12. A hydraulic fluid composition consisting essentially of from 0.01 to 2% by weight of a condensation product of an aminoalkyl silicate selected from the group consisting of a silicate of the formula Si(OR ),,(OR wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl group of from 1 to 6 carbon atoms and x is an integer of from 1 to 4 and a silicate of the formula (R O) (R O) SiO, wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl of from 1 to 6 carbon atoms and y has a value greater than zero and up to 2 and an oxirane compound of the formula wherein R and R are each selected from the group consisting of hydrogen, alkyl of from 1 to 6 carbon atoms, alkenyl of 1 to 6 carbon atoms, a phenyl group, an alkyl-phenyl group wherein the alkyl group is of 1 to 6 carbon atoms and a benzyl group in an organic hydraulic fluid selected from the group consisting of a lower alkylene glycol, a poly lower alkylene glycol, a lower alkylene glycol lIIlOIlO lower alkyl ether and a poly lower alkylene glycol mono lower alkyl ether.

13. A cleaning composition for metal systems carrying liquids, said composition consisting essentially of an aqueous solution of (1) about 2.5% by weight of a watersoluble condensation product of an aminoalkyl silicate selected from the group consisting of a silicate of the formula Si(OR (OR wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl group of from 1 to 6 carbon atoms and x is an integer of from 1 to 4 and a silicate of the formula (R O) (R O) Si0, wherein R is an alkyl group of from 1 to 6 carbon atoms carrying an amino group having at least one hydrogen atom attached to the nitrogen atom, R is an unsubstituted alkyl of from 1 to 6 carbon atoms and y has a value greater than zero and up to 2 and an oxirane compound of the formula wherein R and R are each selected from the group consisting of hydrogen, alkyl of from 1 to 6 carbon atoms, alkenyl of 1 to 6 carbon atoms, a phenyl group, an alkyl-phenyl group wherein the alkyl group is of 1 to 6 carbon atoms and a benzyl group and (2) from 2 to 40% by weight of a highly alkaline salt selected from the group consisting of trisodium phosphate and sodium carbonate.

References Cited UNITED STATES PATENTS 3,110,601 11/1963 Emblem et a1 252-311 3,223,646 12/1965 McKenna et al 252- LEON D. ROSDOL, Primary Examiner.

STANLEY D. SCHWARTZ, Assistant Examiner.

US. Cl. X.R. 

